Help/replacement

[Sitter]

Hi people, I've a bit of a problem with my bike in that a washer I had on the rear derailluers has snapped and come off, I have a replacement, but when trying to unfasten the bolt with my allen key, it keeps slipping and the inside has now lost it's shape so I'm unable to undo it. Thus it appears that the only way to remove it is to saw it off. I was just wondering if anybody knows of anywhere that I could get a replacement from, and what sort of dimensions it should be?

Picture at this link with the offending bolt ringed. It's annoying as without the washer, the derailleur is able to wobble slightly, and so when going up hills or trying to accelerate at times, in certain gears especially, the bike finds it more preferable for the chain to slip!

 

[asterix]

If it were me I'd think of drilling it or using an angle grinder to take off the head.

How did you strip the allen nut?

 

[Amanda P]

I started writing a reply, and then realised that if the bolt is seized in the hanger, you are in for a bit of a do to get it out, and the mangeld bolt head only makes it harder. Presumably it is in there pretty tight, or you wouldn't have managed to mangle the bolt head trying to unscrew it.

It's too late for this bolt, but next time, make sure you have exactly the right sized allen key, and that it's not slipping.

The problem is that if you saw off the bolt, or drill out its head, you'll have very little of it left to grip to unscrew it from the hanger. And if you can't get the bolt out of the hanger, you can't fit a new bolt, or a new derailleur (which I suspect is the best option here). It may be simpler to fit a new hanger as well.

Unless you're a confident engineer (and presumably you wouldn't be asking if you were), I think this is one for your local bike shop. Sorry.

A new derailleur of similar quality to the one in the pic shouldn't be more than about £15, and the job should be easily done in half an hour to an hour, I'd say, by someone with some expertise and the right tools.

 

[Sitter]

I had the right sized allen key, I used it to loosen the thing slightly to have a closer look at the snapped washer in the first place, although it was very stiff the key didn't slip (and I didn't tighten it as much as it was previously). I was leaning towards a new derailleur prior to posting, I was just interested to see if there were any other options people could suggest. Trip to the local bike shop might be in order. Thanks.

 

[mickle]

First of all, throw away your cheap Allen keys and buy a decent set from a bike shop for a tenner. Cheap tools ruin nuts and bolts, look at the head of your 5mm, its all mashed up ain't it? Bin it.

With your new Allen key and a hammer gently tap the tool into the Bolt. If the damage isn't too severe you'll be able to undo it, replace the washer and Bob's your Aunties husband.

If the above doesn't do the trick you'll need to resort to a 'more assertive' strategy. Hack-saw a slot right across the face of the bolt deep enough to take the biggest screwdriver you've got. You'll need to replace the bolt.

If the above doesn't work take it to the LBS. Where they'll suck their teeth and say 'Who's the cowboy that told you to do that?'

No they won't, it's standard procedure and it's easy to do. Honest.

 

[Night Train]

I was going to say saw a slot in it too.

Alternatively saw two flats on to the sides of the head so it takes a spanner. Then use a mole grip on the flats and apply leverage.

Alternatively saw, file or grind the whole head off and remove the mech to leave a stud on the frame. Grip that with mole grips and apply leverage.

Alternatively remove the hanger and replace the whole thing and don't even bother with trying the bolt.

Agree with Mickle on the tools, bad tools are worse then useless as they can cause more harm the good.

 

[Mr Pig]

Alternatively remove the hanger and replace the whole thing and don't even bother with trying the bolt.

That's what I'd do. I'd take the hanger off and bin the lot. Weigh up the twenty quid it'll cost to fit shiny new perfectly working bits verses the hours of hassle you'll have trying to mess around and sort the old one. Factor in the fact that you might kill it in the process and end up needing to buy a new one anyway and it's no contest.

Or you could pay a shop to remove it, which will probably cost as much as buying a new one....